Photovoltaic devices are non-polluting and silent in operation. They are readily adapted to either a centralized, or distributed power generating system and as such, are an attractive alternative to fossil fuels and nuclear power sources. The relatively high cost of photovoltaic power has been a historical limitation upon its use; however, high volume processes for the preparation of thin film semiconductor devices have now dramatically decreased the cost of photovoltaic materials. It is now possible to manufacture thin film photovoltaic devices in a continuous, roll-to-roll processor. U.S. Pat. No.4,485,125, the disclosure of which is incorporated herein by reference, describes one such process.
The output of a typical high volume process comprises a large area roll of substrate material coated with a multiplicity of semiconductor layers thereupon. In order to fabricate a practical device, it is generally necessary to convert the large area material output by the roll-to-roll process into a plurality of discrete devices optimized for particular voltage and power requirements. Processing steps typically include cutting the large area material into smaller area portions, testing the individual portions, applying current collecting structures such as collector grids and bus bars to the individual devices, assembling the devices into power generating modules, and affixing protective and/or support structures to the modules. These subsequent fabrication steps can be labor intensive, and they can possibly compromise the efficiency, and even the operability, of the resultant devices by introducing short circuits, high resistance contacts, and other defects of a like nature. It will thus be appreciated that the processing of the large area material can be a bottleneck which negates many of the benefits of high volume production.
There is a need for a methodology wherein large area bodies of photovoltaic material may be efficiently fabricated into devices specifically adapted for particular end uses. The present invention provides a production line method for device fabrication which is highly efficient, both in terms of required labor, time and the economical use of photovoltaic material. These and other advantages of the present invention will be readily apparent from the drawings, discussion and description which follow.